"It used to be thought that the world was flat. That beyond the horizon lurked a bottomless void, measureless to humans. As our ships got better and our navigators more confident, vessels that disappeared over one horizon began returning triumphant from the other. The Earth was curved, a sphere with no edges. We didn't fall off because a mysterious force called gravity kept everyone and everything stuck to the planet's surface.
"Then Albert Einstein came along and told us that space itself was curved. Now we realise that if we sail off into the sea of curved space we call the Universe, there are indeed bottomless voids that the unwary traveler can fall into - and they are measureless to humans. They lurk on the other side of their own dark horizons, and we call them Black Holes."
-Dr. Richard Smith
A black hole is an astronomical contradiction - a dark star, an invisible nothing. Its end is marked by the so-called "Event Horizon", a circle of darkness that hides the inside and defines the point of no return. There is no solid surface beyond, just a bottomless gravitational spin so strong that it sucks everything - even light - forever inward. Distruction awaits at the center in the form of the Singularity, Gravity’s fatal attractor.
Hidden forever from view, the Singularity marks the spot where a huge gravitational force has been concentrated. All the mass, light and energy that has ever fallen into the black hole is compressed by its own overwhelming gravity into a point that is infinitely small and infinitely dense. The more a black hole swallows, the heavier it becomes, yet the Singularity never changes. Space has been squelched out of existence, and Time, to a stop. Step over the Event Horizon and for all intents and purposes you’ve fallen off the edge of the universe.
"The concept of Gravity, this unseen force that dominates our lives and pulls us eternally towards the ground, has long challenged the greatest human minds. Even in Galileo's day, the tower at Pisa had a good lean to it - perfect for dropping things off. Galileo wondered why no matter how heavy or light objects were, they all took the same amount of time to fall to Earth. He puzzled too about why the planets moved they way they did. His conviction that they orbited around the sun led to house arrest for heresy. He was still trying to put the gravity puzzle together when he died in Florence in 1642.
"On Christmas Day that same year, the gravity baton was handed to Isaac Newton, born weak and premature in a Lincolnshire farmhouse. Twenty three years later, Newton returned to Woolsthorpe Manor to sit out the plague sweeping southern England. With 18 months quiet thought in the countryside he discovered calculus, unravelled the nature of light, and began formulating laws for the motion of the planets: discoveries that still underpin most of modern physics. One day when he was having a short break with a cup of tea, a falling apple interrupted his thoughts and led him to ponder gravity itself.
The reason the apple fell straight down was that it was trying to fall to the centre of the earth where gravitational attraction was focused. And the Earth wasn’t the only object that had gravity, so did the moon, the sun and the planets. In fact, Newton reasoned, every object in the universe - including ourselves - has gravity. The bigger and heavier, the greater it’s gravitational force. We are glued to the surface of the Earth - and not the other way round - only because it is has so much more mass. The Earth orbits around the sun for the same reason. Finally, Newton had found a reason for the heavens to move the way they do."
-Dr. Richard Smith
Spacetime is ‘straight’ only when it doesn’t have anything in it. Wherever there is mass, there is gravity. Wherever there is gravity, space is curved. The curvature of space decides how an object will travel through it. The object will decides how space bends around it. Gravity, according to Einstein, is the curvature of space.
To understand the biggest things in the universe, you need to start with the smallest things. When we found out of the secrets of nuclear energy, scientists finally understood a little as to how black holes might form in nature. Stars are born when huge clouds of cosmic dust and hydrogen begin to clump and condense under their own gravitational weight. Gravity grows stronger by the hour as the increasing density of the protostar curves space more strongly. Faster and faster, the hydrogen gas falls in upon itself in the condensing core. The more it collides the hotter it grows. When the core reaches 10 million degrees, the hydrogen protons begin to fuse into helium. Some of the mass disappears, having being turned into energy and light. Like a giant cosmic light bulb, the star has switched itself on.
A neutron star resists the ongoing crush of gravity, only with its neutrons packed in like sardines. But if the remains of the star after supernova weigh more than three times the mass of the sun, even neutrons cannot hold back the enourmous force of gravity. The neutrons are squashed into oblivion. The star’s core becomes so dense that gravity overwhelms space itself, distorting it so horribly that it, and time with it, is forced off from the outside universe. A darkness forms at the stars' middle and moves relentlessly outwards as the stars brilliance is sucked inwards. This is the hungry, growing thing of a black hole: gravity’s final triumph. There is no escape, no turning back, until the entire mass of the star has been swallowed and its brilliance completely destroyed.
The singularity is where science ends and speculation begins. Space and time have stopped to exist, replaced by a seething chaotic mass we call quantum foam. This bizarre mix is where Einstein’s laws fail. This is where the laws of quantum mechanics fail. This is the realm of something called Quantum Gravity - one of the hottest areas of advanced mathematical research.
"Although black holes have the power to hoover up anything and everything that strays too close, they can’t hunt. Contrary to popular belief, if you replaced our Sun with a black hole of the same mass the Earth wouldn’t get sucked in, there just wouldn’t be any sunlight. You could even orbit a black hole in a spacecraft just so long as you kept a safe distance."
-Dr. Richard Smith
Get too close though and strange things start happening. Space gets stretched longer and skinnier. You would find your feet being pulled miles away in front of you while your body is squeezed sideways. You will have become a piece of space spaghetti long before you reach the event horizon. Then you’d be ruptured into your own fundamental particles and disappear behind the veil of darkness.
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